Method of preventing clogging of the hydrogen inlet to a reducing zone in the reduction of ferrous chloride vapor by hydrogen



March 30, 1954 P. WHITEHOUSE ETAL 2,673,797

METHOD OF PREVENTING CLOGGING OF THE HYDROGEN INLET TO A REDUCING ZONEIN THE REDUCTION Olj FERROUS CHLORIDE VAPOR BY HYDROGEN Filed Jan. 17,1952 IN VEN TORS frw'qf J. WkJe/muse BY Edward 12 find/6r EM JOB'WAWPatented Mar. 30, 1954 METHOD OF PREVENTING CLOGGING OF THE HYDROGENINLET TO A REDUCING ZONE IN THE REDUCTION OF FERROUS CHLORIDE VAPOR BYHYDROGEN Irving P. Whitehouse, South Euclid, and Edward A. Beidler,Columbus, Ohio, assignors, by direct and mesne assignments, to RepublicSteel Corporation, Cleveland, Ohio, a corporation of New JerseyApplication January 17, 1952,. Serial N0. 266,828

5 Claims.

The present invention relates to a method of preventing clogging of thehydrogen inlet to a reducing zone in the reduction of ferrous chloridevapor by hydrogen and, more particularly, such clogging incident to theaccumulation of an adherent. deposit at and adjacent to the hydrogeninlet into such a reducing zone. This clogging tends, in a period oftime, to restrict and eventually to plug this inlet completely. It hasbeen found, in practice, when reducing ferrous chloride vapor in areducing zone with hydrogen, which is separately introduced into thiszone, that a collar of adherent material builds up around the end ofthis inlet, which collar is gradually lengthened; and the aperturetherethrough is gradually constricted until the hydrogen inlet iseventually plugged. This collar appears to be composed of a more or lesssintered body of metallic iron with some solid ferrous chloride therein.If the operation were to be carried on only for a relatively short timeand then the inlet mechanically cleaned in some suitable manner, thedifficulty which thisinvention seeks to overcome would not be of seriousnature. This, however, is difficult to accomplish during the continuedoperation of theapparatus and without disassembly thereof. In the normaloperation of the general process of substantially continuously reducingferrous chloride vapor with hydrogen in 'asubstantially closed reductionzone, as set forth, for example; in the copending application of Crowleyet' al., Serial No. 214,632, filed March 8, 1951, and entitled Processof Reducing Ferrous Chloride inthe Gaseous Phase With Hydrogen toProduce Metallic Iron, the need for the method ofjthe present inventionis apparent, as this process cannot be carried out continuously without,in some.

way overcoming the difficulty of plugging the hydrogen inlet. The;present invention presents a preferred method of accomplishing. thisresult.

Another undesired effect of the operation of the process of the Crowley,et' all application, when the method herein described is not utilizedtherewith, is that the collar, which is formed as aforesaid, around thehydrogen inlet, often does not grow in a direction parallel to thedesired direction of the hydrogen stream, and, therefore tends todeflect the hydrogen stream, so that the'desired impingement of thestream with the stream of ferrous chloride vapor no longer occurs at thepredeterminedpoint in the reduction zone spaced from" both nozzles andfrom the walls of thereduction *zone. For example, if

the point of impingement :of: these streams were 2. changed bydeflecting the hydrogen stream so that this point were too close to awall or the chamber, the resulting solid material, princi pally metalliciron" in powdered form, would tend to collect on the walls of thechamber of the reducing zone and adhere thereto in a manner interferingprogressively with the desired operations. The presentv invention,therefore, has as one of its objects, the prevention of these undesiredoperations.

Summarizing the present invention, therefore,

, inlet hydrogen should not be over about 1000 F. It may be almost anyamount cooler than that, although normally it is never introduced belowroom temperature due to practical difiiculties of cooling the hydrogen.In practice it is preferred to cool the hydrogen with availablecoolingwater from any" available source of water at whatever low temperaturecan be obtained for the hydrogen by such cooling. For example,

temperatures around 160 F. have been easily obtained for the incominghydrogen and have been found to be eminently satisfactory in operation.As the temperature of the hydrogen or hydrogen-containing gas rises,some difliculties' are met with along the lines above outlined, so

that when the temperature of the incoming hy-' drogen is raised to about800 F. one may expect to encounter some difficulties Whenthe temperatureof the incoming hydrogen reaches over about 1000 F., the difficultiesare so pronounced that continuous operations above about thistemperature are considered undesirable and are not included in thepurview of the present invention.

The temperatures of the hydrogen-containing gas as aforesaid arerelatively cool in respect to the average temperatures existing withinthe reducing zone, which should'be maintained by suitable meanssufficiently high so that the vapor pressure of' ferrous chloride willbe substantial. For this purpose, the average temperatures in thereducing zone should be at least about 1250 F. Preferably, however, theaverage temperatures in the reducing zone-will be such that" fera rouschloride'present will be maintained substantially all in vapor form- 1.6., about 1800 F. to about 2000 F;

As: generally suggested above; the present invention is an improvementupon the general process disclosed in Crowley et al. application, SerialNo. 214,632. -As a result, a detailed description of the basic processwill not be repeated here. For the purpose of the present invention, thebasic process may be said to be one in which ferrous chloride vapor issupplied from-a suitable source thereof into a reducing zone, usually,but not necessarily admixed with some one or more relatively inertcarrier gases. Hydrogen is separately supplied to this zone. Thishydrogen also may or may not be admixed with some one or more inertgases. When inert gases are spoken of in this respect, what is meant inany gas or gases which are either inert per se, such as nitrogen, orwhich are inert insofar as the process or processes contemplated andpossible are concerned, so that any amount of such inert gas which maybe present will not in any way interfere with the reactionwhich is totake place.

-It has been found that ferrous chloride and hydrogen under theconditions present in the reducing zone as herein described will reactto gether very rapidly, according to the equation:

It has further been found that this equation will not proceed normallyto 100% completion, but rather will proceed toward some intermediateequilibrium. The numerical value of this equilibrium will depend uponthe average temperature in the reaction zone. However, up to thatequilibrium the reaction occurs very rapidly under the conditionspresently contemplated. This reaction introduces the difficultiesdiscussed above and which are overcome by following the teachings-of thepresent invention.

- It has been found that the reaction set forth above is somewhat.exothermic in character. In addition to the heat available from thereaction, it is usually desired, in accordance with the presentinvention, that the necessary heat required to maintain desired averagetemperatures in this zone be introduced primarily as sensible heat inthe ferrous chloride vapor and/or any inert gas introduced therewith.Thus there is no need for the hydrogen-containing gas to be introducedat a high temperature. It is sometimes desirable to supply some heatexternally tolthe .walls of the reaction chamber.

For thepurpose of the present application, it has beenfound that. thishydrogen-containing gas should preferably be-introduced ata relativelylow temperature in respect to the average temperature in the reducingzone, so that reaction does. not occur until the hydrogen-containinggashas cleared its entrance. port by an appreciable distance... By'maintaining the hydrogen ata low-temperature as. it enters the reactor,the equilibriumfor the reaction by which iron is produced is. such thatno appreciable deposit will form.

The first feature of the present invention to be discussed in detail isthe temperature for the introduction of .the hydrogen-containing gas.Due to the fact that the temperature desired is that of hydrogen as itactually enters into the reducing zone, and as it is practicallyimpossible to determine this temperature per se in an accurate manner byany available means due to e3;- ter-nal influences of an uncontrollablenature, it has been customary in carrying on the process of the=presentinvention to introduce hydrogen through a 4" O. D. tube of goodheat conducting material; as copper, and: having a bare uniniii! sulatedportion extending about A" into the reducing chamber or zone. Athermocouple is used for sensing an index temperature, with its junctionpoint in the hydrogen stream inside of this tube and at a point about/8" from the exit end thereof. In one apparatus used the tube extendedsubstantially vertically down into the reaction chamber and thethermocouple was suspended by its connecting wires in the tube asdescribed. The index temperature as measured by this thermocouple isreasonably characteristic of the temperature of the hydrogen and isbelieved to be some function thereof, although the exact function is notknown.

It is recognized that the index temperatures recorded by thethermocouple used under these circumstances will be affected byradiation from any source to which the thermocouple is exposed in use,including some of the walls of the chamher-defining. the reducing zone,the walls of-the end portion of the hydrogen inlet tube and also some ofthe solid particles of iron in the reducing zone. The indicatedtemperature will be influenced by convection heat transfer from thehydrogen flowing into the reducing zone. However, it has been found inpractice that the temperature as measured by this thermocouple is fairlyindicative of the temperature of the hy drogen to the extent that whenthe temperature measured by this thermocouple is within a cer-v tainrange, or at least below 1000" F. as herein provided, the operations maybe carried on in accordance with the present invention. I

In order that the hydrogen be admitted to the reducing zone at atemperature, measured as hereinabove set forth, which will be within thedesired range in accordance with the present in: vention, it has beenfound necessary to limit the heating up of hydrogen during its passagethrough thewalls of the reducing zone or chamber. .In some cases,hydrogen may be available substantially at room-temperature. As such, itis initially at a temperature which is sufiiciently cool to be effectivein accordance with the present invention. In fact, the present inventioncontemplates the use of hydrogen at temperatures substantially aboveroom temperature as herein specifically set forth. On the other hand, ithas been found that if some means were'not used to limit the heatin upof hydrogen during its passage through the walls of the reducing'zone,the hydrogen will be heatedto such a high temperature that the desiredresults in accordance with the present invention will not be attained.This will be evident from examples hereinafter given.

One way of preventing this undesired heats mg up of the hydrogen is bythe provision of suitable insulation. Another, and in .many, re-I spectsan analogousway, is by preventing the transfer of heat to the hydrogerlduring its passage through the walls by providing an inter-. veningcirculation of a cooling fluid in an annular space surroundingthehydrogen inlet, so as to conduct away heat which would otherwise betransmitted to the hydrogen to heat it up to an undesired extent. Forthis purpose, then, such a circulation of cooling fluid may be utilizedin accordance with the present invention as hereinafter moreparticularly described in connection with the drawings forming a part ofthis application.

From a broad point of view, the desired temperature for thehydrogen-containing gas, measmedias-described, is-any temperature notover about 1000? F. There is no critical ilower limit to thistemperature. The high temperaturezlimit of about 1000 F: is.chosenasnathat at whichxthe difficulties above set. forth become sogreat that the continuous operation of the process ceases to be possibleby reason'of these. diiiiculties.

From a more specific point of view, apreferred range of temperature'forthe hydrogen-containing gas, measured as aforesaid, is from. about 300F. to about 400 F. The preferred limits are chosen as thoseat whichthehydrogen may be available, for example, by cooling with availablecold water andwithout introducing excess cost for refrigeration. Thereis nothing critical about these limits.

In some operations. such as those set forth, for example, in thecopending application of Crowley, Serial No. 2243770, filed May 5, 1951,and entitled Integrated Cyclic Process for Producing Metallic IronFIOZII'II'OILOXidQ Containing Material, hydrogen available in a gaseousmixture at a temperature substantially above the desired temperature.This application discloses an overall cycle in which reduction offerrous chloride vapor with hydrogen is but one phase. The other phasesof this disclosure have no bearing upon the present application.However, wh n the reduction process is used as one phase of this overallcycle, or. some other similar cycle, then the hydrogen available is at atemperature substantially greater than that at which it is desired to beintroduced into the reducing zone, according to the present invention.Under these circumstances, it is usually necessaryto cool the hydrogenby the use of any availab e cooling fluid. such as. cooling water.Usually such cooling water is, available at about room temperature. Anytemperature to which the hydrogen may be cooled by the use of suchcooling water and anv available cooling means such as conventional heatinterchangers, may be used in this connection. It has been found, forexample, that with water at a temperature of about 48 F., hydrogensupplied at room temperature may be prevented from heating up to atemperature over about160 F. The. operation, under these circumstances,is quite satisfactory.

While the process of the present invention may be carried out in anumber of different types of apparatus, which in detail form no part ofthis invention, there is illustrated in the accompanying drawings, in. adiagrammatic manner, an apparatus in which the process may be.carried.out..

In the drawings:

Figure 1 is a view, principally in elevation, but i with parts brokenaway and in vertical section,

of an apparatus in which. the process of. the

presentinvention may be carried out; and

Fig. 2 is anenlarged detailed view of a portion of the constructionshown in Fig. 1, the view being upper. portion of the zone i i and arelatively lower temperature in the lower portion thereof. This type ofarrangement for a reducing zone for conducting the reaction in questionis dis.-

.closed in. greater detail. in the Crowley et. al. application, SerialNo. 214,632, aforesaid.

There isshown a-pipe or conduit-Illeading into the zone II forthezintroductionof ferrous chloride vapor. This vapor maybe generatedinany suitable equipment or produced in any desired manner and supplied ina predetermined directionas'indicated by the arrow [3. The particularmeans shown is intended to be purely diagrammatic rather than structuralas it is immaterial from the point of view of the present applicationWhat structural means are used for the introduction of'the. ferrouschloridevapor into the reducing zone.

Means, hereshown as a duct or tube l4, may be 'used for supplyinghydrogen or a hydrogencontaining gas to the reducing zone I I. In apreferred form of the invention, the hydrogen-containing gas isintroduced in a a direction indicated by the arrow I5, so that itwillintersect the stream of ferrous chloride vapor at a pointl6 centrally ofthe reducing zone as'shown. In-a practical embodiment of the invention,the tube [4 may be of some good heat conducting material, such ascopper, the tube extending as shown at l1 into the reducing zone I about4 inch.

As above set forth,- means are provided for ascertaining and indicatingand/or recording an index temperature, which will be characteristic ofthe temperature of the hydrogen-containing gas per se. For this purpose,a thermocouple l3 may be'used positioned inside of the pro ecting endportion I! of the tube l4-and about inch from the exitend of thistube-Wires Hand 20 leading to the thermocouple-junction l8 may be passed fromthe junction through the tube I4 and thence outside the apparatus in asuitable way to any appropriate'temperature sensing instrument (notshown) for. indicating and/or recording such temperatures, such as areconventionally used withthermocouples.

In. order that thehydrogen-containing gas being suppliedtothereducingzone H be either positively'cooled or be prevented. fromheating up to an undesired extent dueto the heat. picked up'by thetubeMfrom the Wall of the container Ill, or from materials within thereducing zone, a cooling means maybe provided: for the tube I 41 inrtheform ofa jacket 2! through which a cooling fluid may. be passed-betweenan inlet 22 and: an outlet 23;. The cooling fluid will thus preventundesired heating of the tube Mand prevent the building up of. too higha temperature in1the-incoming hydrogen-containing gas passedtherethrough; or, if a relatively hot gas issupplied to thetube: M, thetemperature-controlling fluid passed through the jacket 2| may, in factservepositively to reduce the temperature thereof.

The reducing zone i I may be-provided'with a suitable outlet'sduct- Mfor the.- products of the reactioninthereducingzone, which-may beconveyed'thereby'to any desired point at'which they may. besegregatedand/or utilized.

Considering how the theories underlying the process of the presentinvention, it is' believed that the action, which occurscausing adherentdeposits of some solid material to build up aroundthehydrogen-containing gas inlet, is a premature reaction betweenhydrogen and ferrous chloride, resulting in the production of ironpowder immediately adjacent to the inlet. It is believed that this ironpowder in its nascent state which. it. is initially produced. is verysticky and. will adhere; to. adj acent. relatively, hot. sunfaces.Thisgradual.buildirigbp oi iron...powder my I of an adherent characterserves to build a ring and eventually a tube-like structure probablyconsisting principally of iron powder. There may be, however, some solidferrous chloride admixed with or occluded in this body of iron inpractice. As the building up of an annular body or tube of this materialprogresses, the remaining opening through which the hydrogen-containinggas passes is progresively constricted, until it is altogether stoppedor plugged up.

When operating with relatively pure hydrogen introduced at substantiallythe same temperature as that inside the reducing zone, this completeplugging occurred in a very few minutes as set forth in an examplehereinafter given. If, however, the hydrogen-containing gas beintroduced at relatively lower temperature than that in the reducingzone, in accordance with the present invention, it is believed that thislower temperature serves sufficiently to delay the reaction betweenhydrogen and ferrous chloride, so that the reaction does not occurimmediately adjacent to the hydrogen inlet opening and so that the ironpowder produced will be liberated at a portion of the reducing zonespaced substantially away from this opening and from the walls of thereducing zone, and hence the iron will not adhere thereto as an adherentdeposit as aforesaid. Also the relatively cool hydrogen flowing into thereaction chamber tends to keep the temperature of the hydrogen inletpassage relatively cool, and thus prevents the means forming thispassage from providing heated surfaces to which iron powder formed inthe chamber will easily adhere. It may further be that due to theproduction of the iron powder in suspension in the central portion, forexample, of the reducing zone, that other iron particles tend to buildup on the particles of iron initially produced, resulting in what isequivalent to crystal growth. These larger crystals, grown in this way,may then be relatively non-adherent in character. Due to their greaterweight, these larger crystals may fall freely toward the bottom of thechamber or reducing zone and/or carried out with the exhaust gasespassing therefrom.

While these theories have been set forth herein as the best theoriespresently known, it is pointed out that the present invention does notspecifically rely upon the accuracy of any portion of the theories soexpressed, but rather depends upon the performance of specific anddefinite method steps, which have been particularly taught herein, andwhich will produce the results desired in accordance with the presentinvention irrespective of the theories by which those results may beexplained.

It hasalso been found in independent experiments for the reduction ofsolid ferrous chloride with'hydrogen, that this reaction will not occurto any substantial extent at temperatures of about 700 F. and below. Forthis reason, then. it is believed that if the index temperaturedetermined as aforesaid and the hydrogen temperature per se be kept atabout 700 F. or below, there will be little or no tendency for thereaction to occur immediately adjacent to the nozzle or inlet openingfor the hydrogen-containing gas, even if ferrous chloride were presentin solid form (as it would be at this temperature) at that point in thereaction zone. Under such circumstances, it is believed that adherentsolid deposits could not reasonably form. For this reason, therefore, aparticularly preferred temperature, or temperature range, is when theindex temperature is not over 700 F. and the hydrogen temperature per seprobably somewhat less.

On the other hand, it is normally preferred in the operation of thepresent process to operate with the index and hydrogen-containing gastemperatures as low as can reasonably be attained and maintained usingrelatively inexpensive methods for cooling or for preventing theundesired heating up of the hydrogen-containing gas. ihese methods inthe ordinary practice of the process will involve the use of availablewater, such as tap water, for cooling the hydrogen-containing gas inletpassage, 1. e., for passing through the cooling jacket 2| shown in thedrawings. As set forth in the examples hereinafter given, indextemperatures as low as F. have been attained in the practice of thepresent process, and were found to be desirable in use.

The process or method of the present invention is further illustrated inseveral examples, which follow.

Example I This example illustrates the difiiculties that have beenencountered in attempting to reduce FeClz vapor by means of hydrogenwhere no provisions are made for preventing the hydrogen from heating upto the temperatures maintained in the reduction chamber when it isintroduced therein and/or wherein the hydrogen was introduced at toohigh a temperature.

In an attempt to reduce FeClz vapor by hydrogen, the FeCh vapor wassupplied by flash vaporization, at the rate of 10 liters per minute,into a chamber to which hydrogen was separately introduced as aforesaid.No provision was made for insulating or cooling the pipe through whichthe hydrogen was introduced and, in fact, the hydrogen was preheated toabout the same temperature that was maintained in the reducing zone(1830 F.). It was found after only two minutes of operation in thismanner that the hydrogen inlet became completely plugged with a growthof what appeared to be a mixture of metallic iron containing some solidferrous chloride. This growth completely blocked the hydrogen inlet andprevented any further introduction of hydrogen into the reduction zone,thus making it impossible to carry on the desired reaction in acontinuous manner.

Example II This example illustrates the operation of the process whenprovisions are made for preventing the hydrogen initially supplied atroom temperature from heating up to the temperature of the reducing zonebefore it is introduced thereto.

Using a device similar to that shown in the accompanying drawings,hydrogen initially at room temperature was introduced into the reducingzone H through the tube l4. Ferrous chloride vapor was supplied throughthe pipe I 2. The temperature of the reducing zone H was measured at1920 F.; and the index temperature measured by the thermocouple l8 was160 F. In this example, the tube 14 was made of copper having inchoutside diameter and 1%; inch inside diameter. The hydrogen initiallysupplied at room temperature flowed through pipe [4 at a velocity of30.8 feet per second. Cooling water at an initial temperature of 48 F.was passed into the inlet pipe 22 and through the cooling jacket 2| atthe rate of 0.02 cubic feet per second, and passed out through theoutlet 23 at a tem perature of about 67 F. This considerable rise intemperature proved that a considerable amount Example 'III This.example, which describes an experimental run made overa-period ofabout-seven hours, illustratesthe effect of varying hydrogen inlettemperatures, as indicated by the respective index temperatures, on therate of formation of adherent material on and adjacent to the hydrogeninlet. As the index temperatures increase, the tendency for adherentmaterial to form at the exit end of the hydrogen tube increases. A-though no sharp line of demarcation exists at temperatures above about1000" R, such higher temperatures appear to be less favorable forcontinuous operation because of the greatly increased tendency foradherent deposits to form under such conditions.

In this test a ferrous chloride reduction apparatus having essentiallythe same construction as that shown in the drawings was operated byintroducing ferrous chloride vapor through the pipe 2 at the rate ofabout 9.1 grams per minute. Hydrogen was introduced through the pipe [4at the rate of about 1.4 liters per minute, measured at 70 F. and atatmospheric pressure. The hydrogen tube E4 was of copper and had aninside diameter of inch. The temperature in the reducing zone wasmaintained throughout the run at about 1900" F. to 2000 F. In order tovary the temperature at which the hydrogen entered the reducing zone H,the rate of cooling water through the jacket 2| was decreased gradually,so that the hydrogen temperature, as indicated by the index temperature,could be controlled and was raised in a step-wise manner.

The condition of the end portion ll of the hydrogen tube M wascontinuously observed through a sight glass.

For the first two hours of the run, the rate of cooling water was soregulated as to maintain the index temperature, as indicated by thethermocouple I8, between about 320 F. and 340 F. During this period, thereduction reaction proceeded as desired; and powdered iron was collectedfrom the reaction products emerging from the reducing zone through theoutlet duct 24.

During the next 40 minutes, the rate of introduction of cooling waterwas decreased, so that the index temperature rose to about 410 F. Theexit end portion I! of the hydrogen tube still appeared to be clean andunobstructed.

During the next hour, the index temperature was gradually raised toabout 760 F. and held there for about 5 minutes. At this point, a slightgrowth was observed to form at the exit end of the tube. This materialappeared to be light in color and rather fern-like and feathery inconsistency. It was not troublesome, in that it did not appear to blockoff hydrogen; and pieces of it fell or sloughed off from time to time.

The index temperature was then raised to 800 F. and maintained at thatvalue for about onehalf hour. During this time the light, fern-likedeposit continued to form on the inlet tube; but

n? was not adherent in nature and pieces of it fell or. sloughed offfrom timeto time.

'The index temperature was then raised to about 910 'F. and held therefor about one-half hour. The fern lilre deposit aforesaid formedsomewhat more rapidly under theseconditions, but still did not appear toblock the fiow or" hydrogen.

The index temperatur was then raised, by

adjusting the rate of flow of cooling water, until it was about 970 F.It was held at this temperature for about ten minutes, during whichtlllISthE growth'increased to a length of about twoinehesand width ofjinch. Still the hy-v drogen flowdid nota'ppearlto be restricted andafter aboutten minutes, apiece of the growth about 4 inch long fell off.I

The index temperature was "then gradually raised .during the course ofabout an hour and twenty minutes to about 1100 F. During this time thegrowth increased by about and appeared to be somewhat adherent incharacter; although it still did not completely block ofi the flow ofhydrogen. The index temperature was maintained at about 1100 F. for anadditional 15 minutes, but during this time other operationaldifiiculties became so great that the run was discontinued.

From these observations, it is concluded that at index temperatures(determined as aforesaid) above about 1000 F., formation of adherentdeposits at the exit end of the hydrogen tube are formed so rapidly thatit is believed desirable for the purposes of the present invention, tokeep the index temperature from exceeding about this value for the indextemperature. Although it might be possible to operate for a time withindex temperatures above 1000 F., such high temperatures are deemed tobe undesirable for long continuous operations of the type to which thepresent process is well adapted.

While there has been explained herein the principles of the presentinvention and the limits thereof as far as they are known, and whilecertain equivalents have been set forth herein, other equivalents willbe apparent from the foregoing description to those skilled in the art.We do not wish to be limited, therefore, except by the scope of theappended claims, which are to be construed validly as broadly as thestate of the prior art permits.

What is claimed is:

1. In the reduction of ferrous chloride with hydrogen in a reducing zoneat a relatively high temperature to produce iron and gaseous hydrogenchloride, wherein gaseous ferrous chloride and a gas containing hydrogenare separately introduced into a reducing zone, the method of preventingthe clogging of the inlet into said zone for the hydrogemcontaining gasby adherent solid deposits, which comprises the steps of introducingsaid hydrogen-containing gas into said zone at a temperature such thatthe index temperature (said index temperature being that which is sensedby a thermocouple located at a point inside of and about inch from theend of a tube of good heat conducting material, with said tube extendingabout A; inch into said reducing zone) is not over about 1000 F., andmaintaining the average temperature of the materials in said reducingzone at least about 1250 F.

2. The method according to claim 1, wherein said index temperature isabout 300 F. to about 400 F.

3. The method according to claim 1, wherein said index temperature isnot over about 700 F.

4. The method according to claim 1, wherein the average temperature inthe portion of said zone into which the ferrous chloride vapor and thehydrogen-containing gas are introduced is about 1800 F. to about 2000 F.

5. In the reduction of ferrous chloride with hydrogen in a reducing zoneat a relatively high temperature to produce iron and gaseous hydrogenchloride, wherein gaseous ferrous chloride and a gas containing hydrogenare separately introduced into a reducing zone, the method of preventingthe clogging of the inlet into said zone for the hydrogen-containing gasby adherent solid deposits, which comprises the steps of introducingsaid hydrogen-containing gas into said zone at a temperature such thatthe index temperature (said index temperature being that which is sensedby a thermocouple located at a point inside of and about inch from theend of a tube of good heat conducting material with said tube extendingabout inch into said reducing zone) is about 300 F. to about 400 F. andmaintaining the average temperature in the portion of said zone intowhich the ferrous chloride vapor and the hydrogen-containing gas areintroduced from about 1800 F. to about 2000 F.

IRVING P. WHITEHOUSE. EDWARD A. BEIDLER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,418,148 Williams et a1 Apr. 1, 1947 2,596,072 Graham et a1.May 6, 1952

1. THE REDUCTION OF FERROUS CHLORIDE WITH HYDROGEN IN A REDUCING ZONE ATA RELATIVELY HIGH TEMPERATURE TO PRODUCE IRON AND GASEOUS HYDROGENCHLORIDE, WHEREIN GASEOUS FERROUS CHLORIDE AND A GAS CONTAINING HYDROGENARE SEPARATELY INTRODUCED INTO A REDUCING ZONE, THE METHOD OF PREVENTINGTHE CLOGGING OF THE INLET INTO SAID ZONE FOR THE HYDROGEN-CONTAINING GASBY ADHERENT SOLID DEPOSTIS, WHICH COMPRISES THE STEPS OF INTRODUCINGSAID HYDROGEN-CONTAINING GAS INTO SAID ZONE AT A TEMPERATURE SUCH THATTHE INDEX TEMPERATURE (SAID INDEX TEMPERATURE BEING THAT WHICH IS SENSEDBY A THERMOCOUPLE LOCATED AT A POINT INSIDE OF AND ABOUT 1/8 INCH FROMTHE END OF A TUBE OF GOOD HEAT CONDUCTING MATERIAL, WITH SAID TUBEEXTENDING ABOUT 1/4 INCH INTO SAID REDUCING ZONE) IS NOT OVER ABOUT1000* F., AND MAINTAINING THE AVERAGE TEMPERATURE OF THE MATERIALS INSAID REDUCING ZONE AT LEAST ABOUT 1250* F.